Method for filling a fuel-gas tank with fuel gas, fuel-gas tank and fuel-tank system
Patent Information
- Application Number
- EP2023740964
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-08-08
- Filing Date
- 2023-07-04
- Publication Date
- 2025-06-18
- Estimated Expiration
- 2043-07-04
AI Technical Summary
Fuel gas tanks, particularly those made of carbon fiber reinforced plastic, face overheating issues during refueling due to the negative Joule-Thomson effect of hydrogen, leading to potential damage and inaccurate mass calculations due to limited sensor accessibility and high measurement tolerances, which complicates maintaining temperature limits for safe operation.
Integrating sensors into the refueling path to create a stagnation point for accurate temperature measurement, with one sensor recording the total temperature and another the static temperature, allowing for precise monitoring and calculation of average temperatures to prevent overheating and ensure accurate mass calculations, while also determining flow speed and detecting uncontrolled refueling processes.
This method effectively prevents fuel gas tank overload by accurately monitoring and controlling temperatures, ensuring safe operation and precise mass calculations, reducing the risk of damage and measurement errors, and allowing for plausibility checks during emptying processes.
Smart Images
Figure 1.1
Abstract
Description
[0001] Description
[0002] Title:
[0003] Method for filling a fuel gas tank with fuel gas, fuel gas tank and fuel gas tank system
[0004] The invention relates to a method for filling a fuel gas tank with fuel gas. The fuel gas can be, for example, hydrogen or natural gas. Such fuel gases are required, for example, by fuel cell vehicles or vehicles with gas engines.
[0005] Furthermore, the invention relates to a fuel gas tank for a fuel gas tank system and to a fuel gas tank system with at least one fuel gas tank according to the invention.
[0006] State of the art
[0007] In vehicles powered by a fuel gas such as hydrogen, the fuel gas is typically stored under pressure in a fuel gas tank. With hydrogen, the pressure can be up to 70 MPa. The temperature in the fuel gas tank can rise to 85°C. The temperature limit is generally determined by the material of the fuel gas tank, with carbon fiber reinforced plastic ("CFRP") often being used. When using CFRP material, the plastics required to fix the carbon fibers, particularly synthetic resins, become too soft above 85°C, meaning that the required strength of the fuel gas tank is no longer guaranteed.
[0008] Since hydrogen, for example, exhibits a negative Joule-Thomson effect in the relevant temperature range, it heats up when refueling a fuel gas or hydrogen tank. To prevent damage to the fuel gas tank, hydrogen is cooled to approximately -40°C before refueling. Furthermore, an upwardly angled refueling lance can be used to fill the fuel gas tank; this promotes the mixing of fresh hydrogen with the tank contents and thus reduces heating. As a further measure, the tank temperature can be measured or monitored so that refueling can be aborted if the temperature limit is exceeded. To ensure that the temperature limit is adhered to, the refueling process must be aborted early. High measurement tolerances therefore have a negative impact.Since the mass stored in the fuel gas tank is usually also determined based on the tank temperature, high measurement tolerances can also lead to an incorrectly calculated tank level or an incorrectly calculated remaining range.
[0009] For both purposes, it is therefore desirable to obtain the most accurate information possible about the temperature in a fuel gas tank. However, the locally occurring maximum temperature is crucial for complying with the temperature limit, while the average temperature is more suitable for calculating the stored mass. Reconciling these two requirements is difficult. This is especially true because thermocouples, thermistors, or temperature resistors are typically used for temperature measurement, which can only detect the temperature in their immediate vicinity. Furthermore, the limited accessibility of the tank interior severely restricts the choice of sensor position.
[0010] US 2010 / 0032934 A1 discloses, for example, a fuel gas tank with a tank line and a tank valve for filling the fuel gas tank with fuel gas, as well as a sensor arranged on the tank line for detecting a state variable of the fuel gas. The sensor is positioned such that it is outside the pressure jet that forms when the fuel gas tank is filled with fuel gas. This is intended to increase the sensor's measurement accuracy.
[0011] The present invention is concerned with the object of ensuring compliance with a predetermined temperature limit when filling a storage volume of a fuel gas tank with fuel gas in order to avoid overloading the fuel gas tank.
[0012] To achieve this objective, the method having the features of claim 1 and the fuel gas tank having the features of claim 5 are proposed. Advantageous further developments of the invention can be found in the respective subclaims. Furthermore, a fuel gas tank system comprising at least one fuel gas tank according to the invention is specified.
[0013] Disclosure of the invention
[0014] In the proposed method for filling a storage volume of a fuel gas tank with fuel gas, the fuel gas is introduced into the storage volume via a refueling path with an integrated tank valve. A sensor integrated into the refueling path measures the temperature of the fuel gas in the region of a stagnation point, which is formed by the sensor and / or a support body accommodating the sensor.
[0015] Typically, the flow of fuel gas introduced into the storage volume is first slowed or dammed by a wall surrounding the storage volume, resulting in the fuel gas heating up significantly locally in the area of the wall. This can result in local temperature maxima that exceed a permissible limit, posing the risk of overloading the fuel gas tank. Using the proposed method and the artificial stagnation point created within the refueling path, the occurrence of a local temperature maximum – far from the wall – is relocated to the refueling path and detected by the sensor located there. In this way, compliance with a specified temperature limit can be monitored more easily and reliably to prevent overloading of the fuel gas tank.
[0016] In a further development of the invention, it is proposed that the sensor's measured values be compared with a predetermined temperature limit, and if the temperature limit is exceeded, the refueling process is aborted or interrupted. These additional steps serve to reliably prevent overloading of the fuel gas tank. The predetermined temperature limit is preferably still below the limit specified by the fuel gas tank material.
[0017] Preferably, the temperature of the fuel gas outside the area of the stagnation point, for example in the storage volume, is recorded with the help of a further sensor, and the mean and / or difference value is / are determined from the measured values of both sensors. While the sensor arranged in the area of the stagnation point records a local temperature maximum or the “total temperature”, the “static temperature” can be recorded using the further sensor. For this purpose, the further sensor is arranged outside the area of the stagnation point. By averaging the measured values of both sensors, the mean temperature in the fuel gas tank can be determined, which is required to calculate the stored mass. By calculating the difference value, the flow velocity of the fuel gas when filling the storage volume with fuel gas can also be determined. The mass flow or mass flow rate can then be determined from the flow velocity of the fuel gas.the mass of fuel gas introduced into the storage volume can be calculated.
[0018] As a further development measure, it is therefore proposed that the flow velocity of the fuel gas during a refueling process be derived from the difference value.
[0019] During a refueling process, the total temperature and the static temperature are far apart. This means that the difference between the measured values of the two sensors is large. During a draining process, the opposite is true, provided that the refueling path is not also used for draining. If the difference is small or the measured values of both sensors are close together, this information can be used to verify the plausibility of a draining process.
[0020] If a significantly elevated temperature occurs at the first sensor after a refueling process, an uncontrolled "transfer process" can be assumed within a fuel gas tank system with multiple fuel gas tanks. This means that fuel gas from another fuel gas tank is flowing into the fuel gas tank. In this case, the tank valve can be controlled or closed in such a way that the predefined temperature limit is not exceeded.
[0021] The first sensor for measuring the total temperature is preferably integrated into the refueling path in such a way that, when the flow direction of the fuel gas in the refueling path is reversed, it only measures the static component of the temperature. This means that the first sensor is only directly exposed to the flow in one direction, namely the filling direction. Direct flow to the sensor in the opposite direction to the filling direction can be prevented, in particular, by the support body, which shields the sensor when the flow direction in the refueling path is reversed.
[0022] The ratio of the total temperature to the static temperature depends on the specific geometry and / or the connection of the two sensors. Calibration can reduce any errors in the measurement signals from the two sensors, further increasing measurement accuracy.
[0023] Furthermore, a fuel gas tank for a fuel gas tank system is proposed. The fuel gas tank has a storage volume that can be filled with fuel gas via a refueling path with an integrated tank valve. Furthermore, the fuel gas tank has a sensor integrated into the refueling path for detecting the temperature of the fuel gas. The sensor and / or a support body accommodating the sensor forms a stagnation point in the refueling path, in the region of which a measuring range of the sensor is arranged. This means that the temperature of the fuel gas is measured in the region of the stagnation point, so that the total temperature can be detected with the aid of the sensor.
[0024] The proposed fuel gas tank can therefore be used to implement the method according to the invention described above. Using the fuel gas tank, the same advantages as the method according to the invention described above can be achieved.
[0025] Preferably, the sensor and / or the holding body have an inflow surface that is oriented substantially perpendicular to the flow direction of the fuel gas in the refueling path when filling the storage volume with fuel gas. During filling, the fuel gas is therefore dammed at the inflow surface, so that the inflow surface of the sensor and / or the holding body forms the stagnation point. To detect the temperature of the fuel gas in the region of the stagnation point, the inflow surface of the sensor preferably simultaneously forms the measuring range of the sensor.
[0026] In a further development of the invention, a further sensor is integrated into the refueling path or into the storage volume outside the area of the stagnation point. Due to its positioning outside the area of the stagnation point, the further sensor measures the static temperature in the fuel gas tank. A mean and / or differential value can be calculated from the total temperature measured by the first sensor and the static temperature measured by the further sensor. The mean value provides information about the average temperature in the fuel gas tank, which is required to calculate the stored mass. The differential value can be used to determine the flow velocity of the fuel gas in the filling direction.
[0027] When integrating the additional sensor into the refueling path, it is preferably positioned or aligned such that the fuel gas does not flow directly against it, but rather the fuel gas is guided past the sensor. Unlike the first sensor, the formation of a stagnation point must be avoided in the area of the additional sensor. For this purpose, the sensor can be positioned essentially parallel to the flow direction of the fuel gas. Alternatively, the additional sensor can be positioned not only outside the area of the stagnation point, but also outside the refueling path, ensuring that the static temperature is taken more into account.
[0028] Furthermore, it is proposed that the two sensors be connected via the support body. The support body thus facilitates the installation of the sensors.
[0029] Furthermore, the refueling path is preferably guided, at least in sections, via a pipe extending into the storage volume. The pipe defines a filling direction. Furthermore, the pipe has a defined flow cross-section that simplifies the formation of the stagnation point by the first sensor and / or the holding body. For this purpose, the first sensor and / or the holding body are integrated into the pipe, preferably in such a way that an inflow surface in the filling direction is oriented perpendicular to the flow direction of the fuel gas.
[0030] Advantageously, the refueling path, the tank valve, and the at least one sensor form a tank unit that is inserted, in particular screwed, into a preferably centrally arranged front opening of a wall enclosing the storage volume. As a tank unit, all components can be pre-assembled and inserted into the fuel gas tank as a pre-assembled unit, thus simplifying assembly. At the same time, installation space can be saved. The tank unit can also accommodate further components, for example a further valve and / or a further sensor. Furthermore, the tank unit can have a pipe projecting into the storage volume, over which the refueling path is guided at least in sections, in particular an end section of the refueling path.
[0031] Furthermore, a fuel gas tank system is proposed that comprises at least one fuel gas tank according to the invention. For example, several similar fuel gas tanks can be connected in parallel via a common frame. The frame facilitates the installation of the fuel gas tank system in a vehicle, for example, in a fuel cell vehicle.
[0032] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show:
[0033] Fig. 1 is a schematic longitudinal section through a fuel gas tank according to the invention in the area of a tank unit,
[0034] Fig. 2a)-d) each show a schematic longitudinal section through a holding body with two sensors for a fuel gas tank according to the invention,
[0035] Fig. 3 shows a schematic longitudinal section through a pipe with an integrated holding body and two sensors, and Fig. 4 shows a schematic longitudinal section through a pipe with an integrated holding body and two sensors.
[0036] Detailed description of the drawings
[0037] The fuel gas tank 1 shown in Figure 1 has a wall 12 enclosing a storage volume 2 with an end opening 13 into which a tank unit 11 is inserted. A refueling path 3 with an integrated tank valve 4 for filling the fuel gas tank 1 with fresh fuel gas leads via the tank unit 11. An end section of the refueling path 3 is defined by a pipe 10 protruding into the storage volume 2. Since fuel gas, such as hydrogen, heats up considerably when introduced into the storage volume 2, the temperature of the fuel gas is monitored using sensors 5, 6. A first sensor 5 is used to record the total temperature, while a second sensor 6 is used to record the static temperature.
[0038] To record the total temperature, i.e. a locally occurring maximum temperature, the first sensor 5 is integrated into the pipe 10 in such a way that it is located in the refueling path 3 and is directly exposed to the fuel gas flow in the filling direction. The fuel gas accumulates on an inflow surface 9 of the sensor 5 that is oriented perpendicular to the flow direction of the fuel gas, so that a stagnation point 7 is formed across the inflow surface 9. The second sensor 6 for recording the static temperature is also integrated into the pipe 10, but is oriented in such a way that it is not directly exposed to the flow in the filling direction. This means that no stagnation point is formed by the second sensor 6, but rather the fuel gas can flow past unhindered.
[0039] Of the two sensors 5, 6, at least one sensor 5, 6 can be attached to the pipe 10 indirectly via a holding body 8. This applies in particular to the first sensor 5, since the holding body 8 enables the sensor 5 to be arranged as centrally as possible with respect to the refueling path 3, so that the sensor 5 receives good flow. Depending on the design of the holding body 8, the second sensor 6 can also be integrated into it. Exemplary embodiments can be seen in Figures 2a) to 2d). These show that the second sensor 6 is arranged downstream of the first sensor 5 in the flow direction of the fuel gas, at an angle, in particular at a right angle, so that fuel gas can flow past unhindered. To optimize the flow in the refueling path 3, the holding body 8 upstream of the second sensor 6 can have an outer contour that tapers in the filling direction, for example, conically.If the flow direction of the fuel gas in the refueling path 3 is reversed, the outer contour of the holding body 8 simultaneously ensures that the fuel gas flows past the first sensor 5, so that this too only records the static temperature.
[0040] The first sensor 5 is preferably integrated into the holding body 8 in such a way that the inflow surface 9 of the sensor 5 simultaneously forms the inflow surface 9 of the holding body 8. This can be flat, as shown in Figures 2a) and 2b). However, the inflow surface 9 can also be convex, as shown in Figure 2c), or concave, as shown in Figure 3d). Flow optimization can also be achieved through the shape of the inflow surface 9.
[0041] Figure 3 shows a further holding body 8 with a sensor 5 for detecting the total temperature. The holding body 8 is integrated into the pipe 10 and extends perpendicular to the flow direction 15 of the fuel gas. As Figure 3 shows, a connecting wire 14 can be led via the holding body 8 to the sensor 5 in order to realize the necessary electrical connection of the sensor 5. The second sensor 6 for detecting the static temperature is integrated into the inside of the pipe 10 so that the flow cross-section is not restricted by the second sensor 6. The fuel gas flow thus bypasses the second sensor 6. The connecting wire 14 of the second sensor 6 is led outwards via the holding body 8.
[0042] The embodiment of Figure 4 differs from that of Figure 3 only in that the second sensor 6 is integrated into the outside of the tube 10, so that the static temperature of the fuel gas in the storage volume 2 is detected with the aid of the second sensor 6. The connecting wire 14 is also guided outward through the holding body 8.
Claims
Claims 1. Method for filling a storage volume (2) of a fuel gas tank (1) with fuel gas, in which the fuel gas is introduced into the storage volume (2) via a refueling path (3) with an integrated tank valve (4) and with the aid of a sensor (5) integrated into the refueling path (3) the temperature of the fuel gas is detected in the region of a stagnation point (7), which is formed by the sensor (5) and / or a holding body (8) receiving the sensor (5).
2. Method according to claim 1, characterized in that the measured values of the sensor (5) are compared with a predetermined temperature limit value and if the temperature limit value is exceeded, the refueling process is aborted or interrupted.
3. Method according to claim 1 or 2, characterized in that the temperature of the fuel gas outside the area of the stagnation point (7), for example in the storage volume (2), is detected with the aid of a further sensor (6) and the mean and / or difference value is / are determined from the measured values of both sensors (5, 6).
4. Method according to claim 3, characterized in that the flow velocity of the fuel gas is derived from the difference value.
5. Fuel gas tank (1) for a fuel gas tank system, comprising a storage volume (2) which can be filled with fuel gas via a refueling path (3) with an integrated tank valve (4), further comprising a sensor (5) integrated into the refueling path (3) for detecting the temperature of the fuel gas, wherein the sensor (5) and / or a holding body (8) receiving the sensor (5) in the refueling path (3) has a stagnation point (7) in the area of which a measuring area of the sensor (5) is arranged.
6. Fuel gas tank (1) according to claim 5, characterized in that the sensor (5) and / or the holding body (8) has or have an inflow surface (9) which is oriented substantially perpendicular to the flow direction (15) of the fuel gas in the refueling path (3) when filling the storage volume (2) with fuel gas.
7. Fuel gas tank (1) according to claim 5 or 6, characterized in that outside the area of the stagnation point (7) a further sensor (6) is integrated into the refueling path (3) or into the storage volume (2).
8. Fuel gas tank (1) according to one of claims 5 to 7, characterized in that the refueling path (3) is guided at least in sections via a pipe (10) projecting into the storage volume (2).
9. Fuel gas tank (1) according to one of claims 5 to 8, characterized in that the refueling path (3), the tank valve (4) and the at least one sensor (5, 6) form a tank unit (11) which is inserted, in particular screwed, into a preferably centrally arranged frontal opening (13) of a wall (12) enclosing the storage volume (2).
10. Fuel gas tank system comprising at least one fuel gas tank (1) according to one of claims 5 to 9.